The word 'zombie' is never said throughout the first season. The zombies are either referred to as "Walkers", "Geeks", "Roamers", "Lamebrains", and to the CDC, "Test Subjects".

Actors who played zombies had to go through zombie school to learn how to walk and move like zombies.

There was a lot of controversy about what Jenner actually said to Rick Grimes just before the survivors left the CDC at the end of season one. In the BluRay edition of TWD season one, if you turn the center channel audio up very high, you can actually hear Jenner say: "It's in your blood. We're all carriers." Rick doesn't divulge this information to the other survivors until the end of season two.

Though we saw Michonne at the end of season two, saving Andrea's life, her actor hadn't even been hired when the episode filmed. Actor Danai Gurira has some pretty big shoes to fill, since Michonne is one of the biggest badasses in the comics.

In the world of The Walking Dead, walkers outnumber the living about 5000 to 1.